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    Home > Food News > Food Articles > A new suckling-shaped species in Jehol appears!

    A new suckling-shaped species in Jehol appears!

    • Last Update: 2021-04-17
    • Source: Internet
    • Author: User
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    A new suckling-shaped species in Jehol appears!
    Their front paws can dig holes.
    .
    .




    A new suckling-shaped species in Jehol appears!
    Their front paws can dig holes.
    .
    .
    A new species of suckling-shaped Jehol appears!
    Their front paws can dig holes.
    .
    .


     

    The hands can be grasped, the waist can be straight.
    .
    .
    How the human spine evolved through interaction with the environment, this question has to be answered from mammalian fossils hundreds of millions of years ago.

    On April 7, researchers from the Institute of Vertebrate Paleontology and Paleoanthropology of the Chinese Academy of Sciences (hereinafter referred to as the Institute of Paleospine) and the American Museum of Natural History discovered three columns from the Early Cretaceous Period (about 130-110 million years ago) Fossiomanus senensis and Jueconodon cheni were featured in Nature.
    Researchers compared them with living animals and discovered the polymorphism of the mammalian spine and the reason for the species diversity.

    Ecological restoration of Chinese diggers and Chen's diggertodons (drawn by Zhao Chuang)

    Evidence for the convergent evolution of mammals

    Evidence for the convergent evolution of mammals

    These two new species of mammals come from the "world-class fossil reservoir"-the Jehol Biota in western Liaoning, China.
    Among them, the specimens of Chinese digging animals not only preserve the most complete cranioposterior bones of the three-rowed beasts that have been reported, but also the skeleton mammalian fossils found for the first time in the Jehol Biota.

    Prototype specimens of the Chinese Digger (left) and Chen's Digger (right) (provided by Mao Fangyuan)

    "Chinese digger is a mammalian animal, but it is not a mammal in the traditional sense, but a mammal-like reptile that is closely related to it.
    " explained Meng Jin, one of the corresponding authors of the paper and a researcher at the American Museum of Natural History.
    Mammals is a broader concept.
    It is defined in the phylogenetic framework with the tri-row of dentatodons where the Chinese excavators are located, and includes the branch of living mammals.

    Mao Fangyuan, the first and co-corresponding author of the paper and an associate researcher at the Institute of Paleospine, told the China Science News that the Chen’s digger is a mammal, so from a phylogenetic point of view, the Chinese digger and the Chen’s digger Although beasts live in similar times, their kinship is far apart.

    Mammal phylogenetic framework and differentiation time of main taxa (relaxation analysis of research team members)

    "What's interesting is that their bone morphology is very similar.
    For example, they have the specialization of limb bones that are obviously adapted to digging and burrowing life.
    This is also the first forepaw-digging burrowing mammalian animal found in the Jehol Biota.
    .
    " Mao Fangyuan said.

    From the morphological point of view, the limb bones of these two animals are thick and short, especially the forelimbs, the front paws appear wider, and the claws are long and strong.
    They have a long torso, a stubby and powerful neck, and a small tail.
    These appearance features can effectively reduce resistance and provide convenience for digging.

    Comparison of the teeth and limb bones of Chinese Digger and Chen’s Digger after high-precision (sub-micron level) CT processing (provided by Mao Fangyuan)

    Researchers believe that these are common adaptive changes in the limb bones of excavating burrowing animals, and they are also one of the evidences for the convergent evolution of the two species.

    "Chinese Diggers and Chen's Diggers represent the first known burrowing life types in their respective groups.
    This means that the adaptation and evolution of early mammals has involved the digging and burrowing life seen in mammals today.
    Types also reflect the diversity of early mammals and related taxa evolutionary adaptations.
    " Meng Jin said.

    Why the spine of mammals is different

    Why the spine of mammals is different

    In addition to the common point of burrowing, the Chinese digger and Chen's digger have one thing in common with the spine, that is, the increase in the number of sacral vertebrae.
    The number of anterior sacral vertebrae refers to the sum of the number of thoracic vertebrae, lumbar vertebrae, and sacral vertebrae.
    The reasons for its changes are very complicated.

    Mao Fangyuan introduced that from the perspective of evolution and development, the changes in the mammalian spine are mainly reflected in the deformation and quantitative changes of the spine.

    Deformation refers to the morphological and functional replacement of the spine in two adjacent regions.
    It mainly involves the morphological and functional divisions of the spine, including cervical, thoracic, lumbar, sacral and caudal vertebrae.
    It is mainly regulated by the homologous (Hox) genome.
    Among them, the anterior sacral vertebrae are mainly regulated by the hox4-11 gene; and quantitative change refers to the change in the number of vertebrae, and the segmental clock in the development of the receptor segment is controlled.
    The segmental clock presents a periodic oscillating expression pattern.
    The speed of the cycle controls the number and size of the body segments, which in turn determines the number of spine.

    Researchers found that the ratio of the number of cervical vertebrae to the number of sacral vertebrae (CP, cervical to presacral vertebrae) can be used to estimate the deformation and quantitative change of the spine in the fossil.
    When this ratio decreases and the number of sacral vertebrae increases, it indicates that the spine deformation and quantitative change occur at the same time.

    "The Chinese digger has the smallest CP value known to be a mammalian animal, but it has the largest number of sacral vertebrae, which means that the number of vertebral body segments and the deformation of the vertebral body of the Chinese digger occur at the same time.
    " Mao Fangyuan explained, digging.
    The sharp tooth beast has a similar situation, but the degree of change is relatively low.

    This study found through comparison that the number and morphological changes of mammalian fossils have a similar range of changes to living mammals.
    "This shows that the gene-regulated developmental mechanism observed in living mammals has a certain degree of plasticity, and this mechanism has been formed in the common ancestor of mammals and even earlier groups.
    " Meng Jin said.

    Comparison of the main ecological habits of mammals in the Mesozoic era and the schematic diagram of the evolutionary development mechanism under gene regulation (provided by Mao Fangyuan)

    In addition, the researchers speculate that, from the perspective of biological evolution, the number and morphological changes of species' spine are also related to their ability to adapt to the environment.
    For example, slow-moving species tend to have a significant increase in the number of spine, while cats and other species that require a large amount of back movement during fast running tend to stabilize the number of spine, because too many spine numbers are not conducive to fast running.

    "The plasticity of the developmental mechanism and the pressure caused by the ecological environment together have played a key role in the evolution of the morphological diversity of the spine in mammals.
    " Mao Fangyuan said, "but there are also some phenomena in the fossils that cannot be explained by developmental biology.
    There are also some unknown gene expression regulation mechanisms that need to be continuously explored and resolved in the future.
    "

    She said that at this stage, the research still stays at the basic level such as reporting new specimens.
    In the future, there is still a lot of room for research on the specific morphology of the two specimens, and more in-depth and detailed research can also be carried out with the help of more auxiliary methods such as biostatistics.

    "We hope that more modern biological methods can be incorporated into paleontological research, and we also hope that the reproducibility of paleontological experiments will be higher in the future.
    " Mao Fangyuan said.
    (Source: China Science News, Zhang Sixuan and Hu Minqi)

    Related paper information: org/10.
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    org/10.
    1038/s41586-021-03433-2

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    1038/s41586-021-03433-2" target="_blank">https://doi.
    org/10.
    1038/s41586-021-03433-2
    https://doi.
    org/10.
    1038/s41586-021-03433-2
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